1. Field of the Invention
The invention relates to wireless data communication and, in particular, to a method and apparatus for transporting vehicle position data via the wireless communication network system.
2. Description of Related Art
With the development of wireless networks and the popularity of the Global Positioning System (GPS), a growing number of transportation companies and traffic management departments use wireless networks and the GPS system to determine the real-time location of a moving vehicle.
In such applications, the GPS device equipped on a vehicle can receive satellite signals and can determine the position data representing the position of the vehicle based on the signals. A backend server in charge of determining the position of the vehicle exchanges information with the vehicle through a wireless network. The vehicle needs to continuously transport the position data determined by the GPS device, consuming a large amount of bandwidth of the wireless network.
U.S. patent application US2006/0244587A1 discloses a method and apparatus of transportation of compressed measurement data in order to reduce the amount of measurement data, such as position data, needing to be transported via wireless networks. The means of the method for compressing measurement data is to transport the difference (also known as “residue”) between the current measurement data and the reference data, and convert the difference into a variable-length code using a particular encoding schema, for example, converting an integer “24” as the difference into a binary “1011 0000”. Since what is actually transported is the variable-length code for the difference, the amount of the measurement data needing to be transported is compressed.